Firefox only (Windows/Mac/Linux): The Tabhunter Firefox extension adds quick keyboard-based tab switching to Firefox—sort of like Launchy for Firefox tabs. Just invoke Tabhunter, start typing, and Tabhunter searches for a match through all your tabs.

Tabhunter searches only the titles of your open pages, but the search is very fast and works as advertised. You can invoke Tabhunter from the keyboard (Ctrl+Alt+T by default), start typing, and find the tab you want more quickly than you can likely switch over to your mouse and back.

Granted, Tabhunter is decidedly for keyboard shortcut lovers, but if you fall in that group and you regularly have a browser full o' tabs, it's a great extension. Tabhunter is a free download, works wherever Firefox does. If you're not quite into the idea, I've always liked previously mentioned LastTab for boosting my tab-switching skills. Unfortunately it's been buggy for me ever since Firefox 3, so Tabhunter is a welcome entry. Either way, your mileage may vary. Let's hear what you prefer in the comments.